Exhaust Gas Recirculation: Description and Operation

EGR System Components:

EXHAUST GAS RECIRCULATION:
- A defined quantity of exhaust gas is added to the air/fuel mixture to lower combustion temperatures within the cylinders. These lower combustion temperatures reduce the amount of NOx contained in the exhaust.
- This controlled injection of exhaust gases is employed to adapt the vehicle's emissions under varying load factors.








OBD II CHECKS:
- Opening and closing of the EGR valve as controlled by the EGR temperature sensor (flow and leakage of EGR-System).
- Function of the temperature sensor's and pulse valve electrical circuits as part of the comprehensive component check.

Procedures:
Checking occurs by means of a quick temperature sensor in partial load range. This temperature sensor monitors the temperature in the EGR-channel with active or inactive EGR.
During inactive EGR (e.g. idle) the total temperature corresponds to approximate intake air temperature. With active EGR the absolute temperature in EGR-channel is a higher value, so that the function of the EGR is determined from the EGR,temperature measurement.

EGR Temperature Sensor G98:

Electrical Circuit - EGR Temperature Sensor G98:

EGR TEMPERATURE SENSOR -G98-:
- Sensor is bolted into intake manifold. It monitors temperatures within the manifold during active EGR operation.

Signal Application:
The signal is employed to detect malfunctions in the exhaust-gas recirculation system. It exercises no influence on the control of the EGR itself. Excessive temperature levels indicate that the EGR valve is failing to close, while low temperatures indicate that the EGR valve is failing to open properly. When the EGR valve remains open at idle, rough running is the result.

Effects of Signal Failure:
Sensor failure makes it impossible to detect malfunctions in the EGR system.

EGR Vacuum Regulator N121:

Electrical Circuit - EGR Vacuum Regulator N121:

EGR VACUUM REGULATOR VALVE -N121-:
- The EGR Vacuum Regulator Valve is an electro-pneumatic unit. It converts the timing signal from the engine- management ECM into control vacuum for the EGR valve.

Effects of Signal Failure:
The valve cannot provide correct control of the EGR function unless it receives the timing signal from the ECM.